U.S. patent application number 14/045702 was filed with the patent office on 2014-01-30 for light guide plate, light guide plate manufacturing method, and light guide plate manufacturing apparatus.
This patent application is currently assigned to Jun Sakamoto. The applicant listed for this patent is Jun Sakamoto. Invention is credited to Jun SAKAMOTO, Koji SAKAMOTO.
Application Number | 20140029306 14/045702 |
Document ID | / |
Family ID | 46969199 |
Filed Date | 2014-01-30 |
United States Patent
Application |
20140029306 |
Kind Code |
A1 |
SAKAMOTO; Koji ; et
al. |
January 30, 2014 |
LIGHT GUIDE PLATE, LIGHT GUIDE PLATE MANUFACTURING METHOD, AND
LIGHT GUIDE PLATE MANUFACTURING APPARATUS
Abstract
A light guide pate includes: a light guide member with a light
incident surface and first and second principal surfaces; and first
and second protrusions formed on at least one of the first and
second principal surfaces. When the first principal surface is
viewed in a normal direction, a distance between the light incident
surface and the second protrusion is larger than a distance between
the light incident surface and the first protrusion; each of the
first and second protrusions has a shape, a length of which in an
orthogonal direction orthogonal to a propagation direction of light
incident from the light incident surface increases monotonously in
the propagation direction; and a minimum value of the length of the
second protrusion in the orthogonal direction is larger than a
maximum value of the length of the first protrusion in the
orthogonal direction.
Inventors: |
SAKAMOTO; Koji; (Osaka,
JP) ; SAKAMOTO; Jun; (Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Sakamoto; Jun |
Osaka |
|
JP |
|
|
Assignee: |
Sakamoto; Jun
Osaka
JP
|
Family ID: |
46969199 |
Appl. No.: |
14/045702 |
Filed: |
October 3, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2012/059161 |
Apr 4, 2012 |
|
|
|
14045702 |
|
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|
|
Current U.S.
Class: |
362/621 ;
264/1.24; 425/385 |
Current CPC
Class: |
G02B 6/0036 20130101;
G02B 6/0011 20130101; G02B 6/0061 20130101; G02B 6/0065
20130101 |
Class at
Publication: |
362/621 ;
425/385; 264/1.24 |
International
Class: |
F21V 8/00 20060101
F21V008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 2011 |
JP |
2011-082547 |
Claims
1. A light guide plate, comprising: a light guide member with a
light incident surface, a first principal surface, and a second
principal surface; and a plurality of protrusions formed on at
least one of the first principal surface and the second principal
surface, wherein the plurality of protrusions includes a first
protrusion and a second protrusion, and when the first principal
surface is viewed in a normal direction, a distance between the
light incident surface and the second protrusion is larger than a
distance between the light incident surface and the first
protrusion, each of the first protrusion and the second protrusion
has a shape, a length of which in an orthogonal direction
orthogonal to a propagation direction of light incident from the
light incident surface increases monotonously in the propagation
direction, and a minimum value of the length of the second
protrusion in the orthogonal direction is larger than a maximum
value of the length of the first protrusion in the orthogonal
direction.
2. The light guide plate of claim 1, wherein when the first
principal surface is viewed in the normal direction, each of the
first protrusion and the second protrusion is trapezoidal in
shape.
3. The light guide plate of claim 1, wherein the plurality of
protrusions are made of the same material as the light guide
member.
4. The light guide plate of claim 1, wherein the plurality of
protrusions are made of a material different from a material for
the light guide member.
5. The light guide plate of claim 1, wherein when the first
principal surface is viewed in the normal direction, an area of the
second protrusion is larger than an area of the first
protrusion.
6. The light guide plate of claim 5, wherein when the first
principal surface is viewed in the normal direction, the first
protrusion and the second protrusion are arranged so that
respective centers of the first protrusion and the second
protrusion are aligned in the propagation direction.
7. The light guide plate of claim 1, wherein the light incident
surface includes a first light incident surface and a second light
incident surface different from the first light incident surface,
when the first principal surface is viewed in the normal direction,
protrusions of the plurality of protrusions, which are closer to
the first light incident surface than the second light incident
surface, each has a shape, a length of which in a direction
orthogonal to a first propagation direction of first incident light
incident from the first light incident surface increases
monotonously in the first propagation direction, and when the first
principal surface is viewed in the normal direction, protrusions of
the plurality of protrusions, which are closer to the second light
incident surface than the first light incident surface, each has a
shape, a length of which in a direction orthogonal to a second
propagation direction of second incident light incident from the
second light incident surface increases monotonously in the second
propagation direction.
8. A light guide plate manufacturing apparatus, comprising a
printing roll and a transfer roll, wherein a plurality of recesses
including a first recess and a second recess are formed in a
surface of the printing roll, the first recess and the second
recess are aligned in a predetermined direction, each of the first
recess and the second recess has a shape, a length of which in an
orthogonal direction orthogonal to the predetermined direction
increases monotonously in the predetermined direction, and when the
surface of the printing roll is viewed in a normal direction, a
minimum value of the length of the second recess in the orthogonal
direction is larger than a maximum value of the length of the first
recess in the orthogonal direction.
9. A light guide plate manufacturing method, comprising: preparing
a light guide member with a light incident surface, a first
principal surface, and a second principal surface; and printing a
plurality of protrusions on at least one of the first principal
surface and the second principal surface of the light guide member
by gravure offset printing, wherein in the printing, the plurality
of protrusions include a first protrusion and a second protrusion,
and when the first principal surface is viewed in a normal
direction, a distance between the light incident surface and the
second protrusion is larger than a distance between the light
incident surface and the first protrusion, each of the first
protrusion and the second protrusion has a shape, a length of which
in an orthogonal direction orthogonal to a propagation direction of
light incident from the light incident surface increases
monotonously in the propagation direction, and a minimum value of
the length of the second protrusion in the orthogonal direction is
larger than a maximum value of the length of the first protrusion
in the orthogonal direction.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of International
Application No. PCT/JP2012/059161, filed Apr. 4, 2012, which claims
priority to Japanese Patent Application No. 2011-082547, filed Apr.
4, 2011. The contents of these applications are incorporated herein
by reference in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to light guide plates, light
guide plate manufacturing methods, and light guide plate
manufacturing apparatuses.
BACKGROUND ART
[0003] Light guide plates can emit incident light substantially
uniformly from a comparatively wide light emitting surface and are
therefore employed in liquid crystal display devices, illumination
devices, etc. When light from a light source enters a light
incident surface on one side of a light guide plate, the light
repeats reflection on a pair of principal surfaces of the light
guide plate to propagate within the light guide palate in a
direction (propagation direction) substantially orthogonal to the
light incident surface. The light propagating in the light guide
plate is emitted little by little from the light emitting surface
by an optical operation as it propagates. It is noted that in
typical liquid crystal display devices, a diffuser plate is
provided between the light guide plate and a liquid crystal display
element, thereby irradiating the light from the light source
uniformly to the liquid crystal display element.
[0004] It has been known that a pattern of dots, in which the areas
of the dots increase away from the light incident surface, is
provided on a principal surface of the light guide plate (Patent
Literatures 1 and 2). Patent Literature 1 discloses that a pattern
of circular dots is formed on an emission surface or a surface
opposite to the emission surface. Further, Patent Literature 2
discloses that projections and recesses are formed in an emission
surface or a surface opposite to the emission surface with the use
of a mold.
CITATION LIST
Patent Literature
[Patent Literature 1] Japanese Patent Application Laid-Open
Publication No. 5-313017
[Patent Literature 2] Japanese Patent Application Laid-Open
Publication No. 5-210014
SUMMARY OF INVENTION
Technical Problem
[0005] The light guide plates in Patent Literatures 1 and 2 may
exhibit insufficient diffusion efficiency. For example, a demand
for reduction in size of devices is recently increasing more and
more. The present inventors have found that it is necessary to
further increase the diffusion efficiency of the light guide plate
in seeking reduction in thickness of the light guide plate.
[0006] The present invention has been made in view of the foregoing
and has its object of providing a light guide plate that can
exhibit increased diffusion efficiency and a light guide plate
manufacturing method and a light guide plate manufacturing
apparatus, which are suitable for manufacture of such a light guide
plate.
Solution to Problem
[0007] A light guide plate according to the present invention
includes: a light guide member with a light incident surface, a
first principal surface, and a second principal surface; and a
plurality of protrusions formed on at least one of the first
principal surface and the second principal surface. The plurality
of protrusions includes a first protrusion and a second protrusion.
When the first principal surface is viewed in a normal direction, a
distance between the light incident surface and the second
protrusion is larger than a distance between the light incident
surface and the first protrusion; each of the first protrusion and
the second protrusion has a shape, a length of which in an
orthogonal direction orthogonal to a propagation direction of light
incident from the light incident surface increases monotonously in
the propagation direction; and a minimum value of the length of the
second protrusion in the orthogonal direction is larger than a
maximum value of the length of the first protrusion in the
orthogonal direction.
[0008] In one embodiment, when the first principal surface is
viewed in the normal direction, each of the first protrusion and
the second protrusion is trapezoidal in shape.
[0009] In one embodiment, the plurality of protrusions are made of
the same material as the light guide member.
[0010] In one embodiment, the plurality of protrusions are made of
a material different from a material for the light guide
member.
[0011] In one embodiment, when the first principal surface is
viewed in the normal direction, an area of the second protrusion is
larger than an area of the first protrusion.
[0012] In one embodiment, when the first principal surface is
viewed in the normal direction, the first protrusion and the second
protrusion are arranged so that respective centers of the first
protrusion and the second protrusion are aligned in the propagation
direction.
[0013] In one embodiment, the light incident surface includes a
first light incident surface and a second light incident surface
different from the first light incident surface. When the first
principal surface is viewed in the normal direction, protrusions of
the plurality of protrusions, which are closer to the first light
incident surface than the second light incident surface, each has a
shape, a length of which in a direction orthogonal to a first
propagation direction of first incident light incident from the
first light incident surface increases monotonously in the first
propagation direction. When the first principal surface is viewed
in the normal direction, protrusions of the plurality of
protrusions, which are closer to the second light incident surface
than the first light incident surface, each has a shape, a length
of which in a direction orthogonal to a second propagation
direction of second incident light incident from the second light
incident surface increases monotonously in the second propagation
direction.
[0014] A light guide plate manufacturing apparatus according to the
present invention includes a printing roll and a transfer roll. A
plurality of recesses including a first recess and a second recess
are formed in a surface of the printing roll. The first recess and
the second recess are aligned in a predetermined direction. Each of
the first recess and the second recess has a shape, a length of
which in an orthogonal direction orthogonal to the predetermined
direction increases monotonously in the predetermined direction.
When the surface of the printing roll is viewed in a normal
direction, a minimum value of the length of the second recess in
the orthogonal direction is larger than a maximum value of the
length of the first recess in the orthogonal direction.
[0015] A light guide plate manufacturing method according to the
present invention includes: preparing a light guide member with a
light incident surface, a first principal surface, and a second
principal surface; and printing a plurality of protrusions on at
least one of the first principal surface and the second principal
surface of the light guide member by gravure offset printing. In
the printing, the plurality of protrusions include a first
protrusion and a second protrusion. When the first principal
surface is viewed in a normal direction, a distance between the
light incident surface and the second protrusion is larger than a
distance between the light incident surface and the first
protrusion, each of the first protrusion and the second protrusion
has a shape, a length of which in an orthogonal direction
orthogonal to a propagation direction of light incident from the
light incident surface increases monotonously in the propagation
direction, and a minimum value of the length of the second
protrusion in the orthogonal direction is larger than a maximum
value of the length of the first protrusion in the orthogonal
direction.
Advantageous Effects of Invention
[0016] According to the present invention, diffusion efficiency of
the light guide plate can be increased.
BRIEF DESCRIPTION OF DRAWINGS
[0017] FIG. 1A is a schematic cross sectional view of a light guide
plate according to one embodiment of the present invention, and
FIG. 1B is a schematic top view of FIG. 1A.
[0018] FIG. 2 is a schematic enlarged view of the light guide plate
according to the present embodiment.
[0019] FIG. 3A is a schematic cross sectional view of a light guide
plate according to Comparative Example, and FIG. 3B is a top
schematic view of FIG. 3A.
[0020] FIG. 4A is a schematic enlarged partial view of the light
guide plate according to Comparative Example, and FIG. 4B is a
schematic enlarged partial view of the light guide plate according
to the present embodiment.
[0021] FIG. 5 is a schematic illustration of a liquid crystal
display device including the light guide plate shown in FIG. 1.
[0022] FIG. 6 is a schematic cross sectional view of the light
guide plate according to the present embodiment.
[0023] FIG. 7 is a schematic cross sectional view of the light
guide plate according to the present embodiment.
[0024] FIG. 8 is a schematic top view of the light guide plate
according to the present embodiment.
[0025] FIG. 9A is a schematic illustration of a light guide plate
manufacturing apparatus according to one embodiment of the present
invention, and FIG. 9B is a schematic illustration of a printing
roll in the light guide plate manufacturing apparatus of FIG.
9A.
[0026] FIG. 10 is a schematic illustration of the light guide plate
manufacturing apparatus according to the present embodiment.
[0027] FIGS. 11A and 11B are schematic illustrations for explaining
a light guide plate manufacturing method according to the present
invention.
DESCRIPTION OF EMBODIMENTS
[0028] A light guide plate, a light guide plate manufacturing
method, and a light guide manufacturing apparatus according to
embodiments of the present invention will be described below with
reference to the accompanying drawings. It should be noted that the
present invention is not limited to the following embodiments.
[0029] A light guide plate 10 according to one embodiment of the
present invention will be described with reference to FIG. 1. FIGS.
1A and 1B are a schematic cross sectional view and a schematic top
view, respectively, showing a light guide plate 10 according to the
present embodiment. FIGS. 1A shows a cross section taken along the
line IA-IA in FIG. 1B
[0030] The light guide plate 10 includes a light guide member 20
and a plurality of protrusions 30. The light guide member 20 has a
light incident surface 22 and principal surfaces 24a and 24b. Here,
both the principal surfaces 24a and 24b of the light guide member
20 are substantially planar. The light guide member 20 has a
substantially constant thickness. Typically, the areas of the
principal surfaces 24a and 24b of the light guide member 20 are the
same.
[0031] The light guide member 20 is made of acrylic resin, for
example. The light incident surface 22 of the light guide member 20
faces a light source (not shown in FIG. 1). Light from the light
source enters the interior of the light guide member 20 from the
light incident surface 22 of the light guide member 20 and
propagates in a propagation direction P, as indicated by the arrow
Li in FIG. 1B. In the process of propagation of the light in the
light guide member 20 in the propagation direction P, the light is
emitted from the principal surface 24a of the light guide member
20, as indicated by the allow Lo in FIG. 1A. It is noted that in
the following description of the present specification, the
principal surfaces 24a and 24b may be referred to as a first
principal surface 24a and a second principal surface 24b,
respectively.
[0032] The protrusions 30 are formed on at least one of the first
principal surface 24a and the second principal surface 24b of the
light guide member 20. In the light guide plate 10 shown in FIG. 1,
the protrusions 30 are formed on the principal surface 24a of the
light guide member 20. The protrusions 30 herein are made of a
material different from the material for the light guide member 20.
Accordingly, the refractive index changes in the interface between
the principal surface 24a of the light guide member 20 and each
protrusion 30.
[0033] The protrusions 30 are made of acryl based resin, for
example. Alternatively, the protrusions 30 may be made of polyimide
based resin. Or, the protrusions 30 may include beads. For example,
the beads are made of amorphous silica or acryl and have an average
particle size of about 1 .mu.m.
[0034] Here, the light entering the interface between the light
guide member 20 and each protrusion 30 at the principal surface 24a
of the light guide member 20 diffuses in the interface between the
light guide member 20 and each protrusion 30. Further, the light
diffuses in the interface between each protrusion 30 and a
substance (typically air) around the light guide member 20 and the
protrusions 30. In the light guide plate 10 of the present
embodiment, the protrusions 30 are different in size according to
their positions on the principal surface 24a. The areas of the
protrusions 30 when the principal surface 24a is viewed in the
normal direction are set so as to be increasingly large away from
the light incident surface 22. In general, light incident in a
light incident surface of a light guide plate is emitted from the
light guide plate to be decreased as the propagation length becomes
long. Accordingly, the intensity of the light emitted from the
light guide plate decreases away from the light incident surface.
However, in the light guide plate 10 of the present embodiment, the
protrusions 30 are arranged so that the areas increase away from
the light incident surface 22. Thus, the intensity of the light
from the light guide plate 10 can be uniformed.
[0035] Further, the protrusions 30 herein are arranged in the
propagation direction P. Specifically, when the principal surface
24a of the light guide member 20 is viewed in the normal direction,
the respective centers of the protrusions 30 are linearly aligned
substantially in the propagation direction P. For example, the
distance between the respective centers of adjacent sets of
linearly aligned protrusions 30 is substantially equal to the
length of the largest protrusion 30 in the x direction.
[0036] For example, the length of the smallest protrusion 30 in the
x direction is 20 .mu.m, while the length of the largest protrusion
30 in the x direction is 120 .mu.m. Further, the length (width) of
each protrusion 30 in the y direction is 50 .mu.m or larger and 150
.mu.m or smaller, for example. All the protrusions 30 may have the
same length (width) in the y direction. Furthermore, the thickness
(length in the z direction) of the protrusions 30 is preferably 2
.mu.m or larger and 6 .mu.m or smaller, and more preferably 3 .mu.m
or larger and 5 .mu.m or smaller, for example. Although description
will be made later in detail, such minute protrusions can be formed
suitably by gravure offset printing. The minute protrusions 30 can
appropriately diffuse light, so that a diffuser plate can be
dispensed with.
[0037] The focus will be placed herein upon two adjacent
protrusions 30a and 30b aligned in a single straight line (straight
line in the y direction). When the principal surface 24a of the
light guide member 20 is viewed in the normal direction, the
distance between the protrusion 30b and the light incident surface
22 is larger than the distance between the protrusion 30a and the
light incident surface 22. Herein, each of the protrusions 30a and
30b is trapezoidal in shape. It is noted that in the following
description of the present specification, the protrusions 30a and
30b may be referred to as a first protrusion 30a and a second
protrusion 30b, respectively.
[0038] As described above, the protrusion 30a and the protrusion
30b are arranged so that the respective centers of the protrusion
30a and the protrusion 30b are aligned in the propagation direction
P of the light incident from the light incident surface 22. When
the principal surface 24a of the light guide member 20 is viewed in
the normal direction, each of the first and second protrusions 30a
and 30b has a shape, the length of which in an orthogonal direction
Q orthogonal to the propagation direction P of the light increases
monotonously in the propagation direction P. Accordingly, in the
light guide plate 10 according to the present embodiment, even when
attention is directed locally to the vicinity of each protrusion 30
as well as to the principal surface 24a as a whole, the areas of
the protrusions 30 increase away from the light incident surface
22. Thus, the intensity of the light emitted from the light guide
plate 10 can be further uniformed.
[0039] Moreover, in the light guide plate 10 according to the
present embodiment, the minimum value of the length of the
protrusion 30b in the orthogonal direction Q is larger than the
maximum value of the length of the protrusion 30a in the orthogonal
direction Q. Accordingly, in the light guide plate 10 of the
present embodiment, even when attention is directed locally to the
vicinity of adjacent two protrusions 30, as well as to the
principal surface 24a as a whole, the area of the region where each
protrusion 30 is formed increases away from the light incident
surface 22. Accordingly, the intensity of the light emitted from
the light guide plate 10 can be further uniformed. Arrangement of
the protrusions 30 as above can increase the diffusion efficiency
of the light guide plate 10 of the present embodiment.
[0040] FIG. 2 is an enlarged view of protrusions 30 in one row.
Each of the protrusions 30 is trapezoidal in shape. Lateral sides
of each individual protrusion 30 are aligned in the same straight
lines. As described above, the protrusion 30b has a shape, the
length of which in the orthogonal direction Q orthogonal to the
light propagation direction P increases monotonously in the
propagation direction P. The minimum value and the maximum value of
the length in the orthogonal direction Q (x direction) are denoted
by Lx1 and Lx2, respectively.
[0041] It is noted that the length of at least one of the
protrusions 30 in the propagation direction P (y direction) is
smaller than the maximum value of the length thereof in the
orthogonal direction Q (x direction). Further, preferably, the
length of the one protrusion 30 in the propagation direction P (y
direction) is smaller than the minimum value of the length thereof
in the orthogonal direction Q (x direction). For example, as shown
in FIG. 2, the length Ly of the protrusion 30b in the propagation
direction P (y direction) is smaller than Lx1 and Lx2.
[0042] Comparison will be made below between the light guide plate
according to the present embodiment and a light guide plate
according to Comparative Example. A light guide plate 70 according
to Comparative Example will be described with reference to FIG. 3.
FIGS. 3A and 3B are a schematic cross sectional view and a
schematic top view of the light guide plate 70, respectively.
[0043] The light guide plate 70 includes a light guide member 80
and protrusions 90. The light guide member 80 has a light incident
surface 82 and principal surfaces 84a and 84b. The protrusions 90
are formed on the principal surface 84a of the light guide member
80. When the principal surface 84a of the light guide member 80 is
viewed in the normal direction, each protrusion 90 is circular in
shape. The areas of the protrusions 90 increase away from the light
incident surface 82.
[0044] The areas of the protrusions 90 increase away from the light
incident surface 82 also in the light guide plate 70 in Comparative
Example to obtain uniform emitted light. However, in the light
guide plate 70 of Comparative Example, where the light guide member
80 is reduced in thickness, irregularity in light from the light
guide plate 70 may be observed. For example, when the light guide
member 80 was reduced in thickness from 4 mm to 2.5 mm, light
irregularity was observed in light guide plate 70. By contrast, in
the light guide plate 10 according to the present embodiment, even
when the light guide member 20 was reduced in thickness to 2.5 mm,
no light irregularity was observed.
[0045] The detailed reason thereof is not clear but may be
considered as follows. FIG. 4A shows two protrusions 90a and 90b of
the light guide plate 70 in Comparative Example. When the principal
surface 84a of the light guide member 80 is viewed in the normal
direction, the distance between the light incident surface 82 and
the protrusion 90b is larger than the distance between the light
incident surface 82 and the protrusion 90a. The diameter of the
protrusion 90b is larger than that of the protrusion 90a.
[0046] FIG. 4B is a schematic enlarged partial view of the light
guide plate 10 according to the present embodiment. The focus will
be placed herein also upon the two protrusions 30a and 30b aligned
in the propagation direction P. Here, attention is directed to
regions A, in which light propagating in the propagation direction
P from the light incident surfaces 22 and 82 does not travel over
the corresponding protrusions 30a and 90a but travels over the
corresponding protrusions 30b and 90b when the principal surfaces
24a and 84a of the respective light guide plates 10 and 70 are
viewed in the normal direction. In the light guide plate 70 of
Comparative Example, it is required to form the protrusion 90b
having a relatively large area in order to reserve the region A. By
contrast, in the light guide plate 10 of the present embodiment,
the area of the protrusion 30b can be set relatively small for
reservation of the region A. For this reason, an increase in
diffusion efficiency might be achieved in the light guide plate 10
of the present embodiment.
[0047] Such the light guide plate 10 can be suitably employed in
liquid crystal display devices. With reference to FIG. 5,
description will be made about a liquid crystal display device
100.
[0048] FIG. 5 is a schematic illustration of the liquid crystal
display device 100 including the light guide plate 10. The liquid
crystal display device 100 includes a light source 110 and a liquid
crystal display element 120 in addition to the light guide plate
10. The liquid crystal display element 120 is arranged on the side
of the principal surface 24a of the light guide member 20 of the
light guide plate 10. It is noted that although a diffuser plate is
dispensed with because the light guide plate 10 has a high
diffusing function as described above, the diffuser plate may be
provided between the light guide plate 10 and the liquid crystal
display element 120 as needed.
[0049] The liquid crystal display element 120 includes a front
substrate 122, a back substrate 124, and a liquid crystal layer 126
provided between the front substrate 122 and the back substrate
124. Although not shown herein, the front substrate 122 and the
back substrate 124 each are provided with an electrode, an
insulating layer, a color filter, and the like, as needed.
[0050] Light emitted from the light source 110 enters the light
incident surface 22 of the light guide plate 10 and propagates in
the interior of the light guide plate 10 in the propagation
direction P. In the light guide plate 10, the light is emitted
toward the liquid crystal display element 120 from the principal
surface 24a of the light guide member 20. The liquid crystal
display element 120 modulates the light emitted from the light
source 110 through the light guide plate 10, thereby performing
desired display.
[0051] It is noted that the liquid crystal display device 100 may
further include a reflector plate 130. The reflector plate 130
reflects the light emitted outward from the principal surface 24b
of the light guide member 20 to return the light to the light guide
member 20. Thus, utilization efficiency of the light emitted from
the light source 110 can be increased.
[0052] It is noted that although the liquid crystal display device
100 including the light guide plate 10 is described as one example
herein, utilization of the light guide plate 10 is not limited to
the liquid crystal display devices. For example, the light guide
plate 10 may be employed in illumination devices. Alternatively,
the light guide plate 10 may be employed in any other devices.
[0053] Although the protrusions 30 are made of a material different
from the material for the light guide member 20 in the above
description, the present invention is not limited to this. The
protrusions 30 may be made of almost the same material as the light
guide member 20.
[0054] FIG. 6 is a schematic illustration of a light guide plate 10
according to the present embodiment. The protrusions 30 herein are
made of almost the same material as the light guide member 20.
Accordingly, the refractive index changes little in the interface
between the principal surface 24a of the light guide member 20 and
each protrusion 30. However, since the protrusions 30 are formed on
the principal surface 24a of the light guide member 20, light
diffuses in the interface between each protrusion 30 and a
substance (typically, air) around the light guide member 20 and the
protrusions 30. It is noted that in this light guide plate 10, the
protrusions 30 may be formed integrally with the light guide member
20. Such the light guide plate 10 can be suitably manufactured
using a mold.
[0055] As described above, the protrusions 30 may be made of the
same material as the light guide member 20 or another material.
However, where the protrusions 30 are made of a material different
from the material for the light guide member 20, a great advantage
in diffusion can be achieved. The refractive index of the
protrusions 30 is preferably higher than the refractive index of
the light guide member 20. However, the refractive index of the
protrusions 30 may be lower than the refractive index of the light
guide member 20.
[0056] It is noted that the protrusions 30 are formed on the
principal surface 24a of the light guide member 20 in the above
description, which however, should not be taken to limit the
present invention. The protrusions 30 may be formed on the
principal surface 24b of the light guide member 20.
[0057] FIG. 7 is a schematic illustration of a light guide plate 10
according to the present embodiment. The protrusions 30 herein are
formed on the principal surface 24b of the light guide member 20.
It is noted that the protrusions 30 may be made of a material
different from the material for the light guide member 20 or made
of almost the same material as the light guide member 20.
[0058] As shown, the protrusions 30 may be formed on one of the
principal surface 24a and the principal surface 24b. Alternatively,
though not shown, the protrusions 30 may be formed on each of the
principal surface 24a and the principal surface 24b.
[0059] It is noted that the light guide member 20 has a
substantially constant thickness in the above description, which
however, should not be taken to limit the present invention. The
light guide member 20 may vary in thickness according to position.
For example, the light guide member 20 may become thin away from
the light incident surface 22. Further, the areas of the principal
surfaces 24a and 24b are substantially the same in the above
description, which however, should not be taken to limit the
present invention. The principal surfaces 24a and 24b may be
different in area from each other.
[0060] The light incident surface 22 is provided on one side
surface of the light guide member 20 in the above description,
which however, should not be taken to limit the present
invention.
[0061] FIG. 8 is a schematic illustration of a light guide plate
10. Light enters the light guide member 20 from each of the light
incident surface 22a and the light incident surface 22b. For
example, the light incident surface 22a is formed at the side of
the light guide member 20 in the negative y direction, while the
light incident surface 22b is formed at the side of the light guide
member 20 in the positive y direction. It is noted that in the
following description of the present specification, the light
incident surfaces 22a and 22b may be referred to as a first light
incident surface 22a and a second light incident surface 22b,
respectively. Further, light incident from the first light incident
surface 22a and light incident from the second light incident
surface 22b may be referred to as first incident light and second
incident light, respectively.
[0062] Here, when the principal surface 24a is viewed in the normal
direction, protrusions of the protrusions 30, which are closer to
the first light incident surface 22a than the second light incident
surface 22b, may be referred to as protrusions 30A (first
protrusion group 30A). Also, protrusions of the protrusions 30,
which are closer to the light incident surface 22b than the light
incident surface 22a, may be referred to as protrusions 30B (second
protrusion group 30B). Each protrusion 30A has a shape, the length
of which in an orthogonal direction Q1 orthogonal to a propagation
direction P1 of the first incident light increases monotonously in
the propagation direction P1. Each protrusion 30B has a shape, the
length of which in an orthogonal direction Q2 orthogonal to a
propagation direction P2 of the second incident light increases
monotonously in the propagation direction P2.
[0063] As described above, the light guide plate 10 may be formed
using a mold, for example. In this case, typically, the protrusions
30 are made of the same material as the light guide member 20.
Alternatively, the protrusions 30 may be formed on the light guide
member 20 by gravure offset printing, screen printing, or stamp
printing. Or, they may be formed by another scheme. It is noted
that the protrusions 30 of the light guide plate 10 are preferably
formed by gravure offset printing.
[0064] With reference to FIGS. 9 and 10, a light guide plate
manufacturing apparatus according to the present embodiment of the
present disclosure will be described below. FIG. 9A is a schematic
illustration of a light guide plate manufacturing apparatus 200
according to the present embodiment. The light guide plate
manufacturing apparatus 200 manufactures the light guide plate 10
by gravure offset printing. In the following description, the light
guide plate manufacturing apparatus 200 may be merely referred to
as a manufacturing device 200.
[0065] The manufacturing apparatus 200 includes a printing roll 210
and a transfer roll 220. The printing roll 210 and the transfer
roll 220 are rotatable. Here, the diameters of the printing roll
210 and the transfer roll 220 are substantially the same. The
surface of the printing roll 210 is subjected to metal plating.
Typically, grooves in a predetermined pattern are formed in the
printing roll 210. This pattern corresponds to lines, figures,
design, or the like to be printed on the light guide member 20. A
blanket is provided on the surface of the transfer roll 220.
Typically, the blanket is made of rubber. For example, the blanket
is made of silicone rubber. Printing is performed by rotating both
the printing roll 210 and the transfer roll 220. Ink is transferred
from the printing roll 210 to the light guide member 20 via the
transfer roll 220. In this manner, ink printing is performed.
[0066] FIG. 9B is a schematic illustration of the printing roll
210. A plurality of recesses 212 are formed in the surface of the
printing roll 210. The focus will be placed herein upon adjacent
two recesses 212a and 212b. In the following description of the
present specification, the recesses 212a and 212b may be referred
to as a first recess 212a and a second recess 212b,
respectively.
[0067] The first recess 212a and the second recess 212b are aligned
in a direction R. When the surface of the printing roll 210 is
viewed in the normal direction, each of the recesses 212a and 212b
has a shape, the length of which in the orthogonal direction Q
orthogonal to the direction R increases monotonously in the
direction R. When the surface of the printing roll 210 is viewed in
the normal direction, the minimum value of the length of the recess
212b in the orthogonal direction Q is larger than the maximum value
of the length of the recess 212a in the orthogonal direction Q.
[0068] It is noted that in FIG. 9B, the recesses 212a and 212b,
which are arranged linearly, are aligned in the direction R
parallel to the rotation direction of the printing roll 21, which
however, should not be taken to limit the present invention. The
direction R in which the linearly arranged recesses 212a and 212b
are arranged may be parallel to the direction of the generating
line of the columnar printing roll 210.
[0069] The light guide member 20 is preferably conveyed to the site
of the printing roll 210 and the transfer roll 220 in the
manufacturing apparatus 200. For example, as shown in FIG. 10, the
manufacturing apparatus 200 may further include a conveyance
section 230 to convey the light guide member 20. The conveyance
section 230 herein is a conveyor. The conveyor 230 conveys the
light guide member 20 toward the fixed printing roll 210 and the
fixed transfer roll 220. The manufacturing apparatus 200 may
further includes a dryer 240 to dry the ink.
[0070] With reference to FIGS. 9-11, one example of a method for
manufacturing the light guide plate 10 will be described below. As
shown in FIG. 11A, the light guide member 20 with the light
incident surface 22 and the principal surfaces 24a and 24b is
prepared.
[0071] As shown in FIG. 11B, ink is printed on the principal
surface 24a of the light guide member 20 by gravure offset printing
to form the plurality of protrusions 30. For example, the
protrusions 30 may be made of acrylic resin. It is noted that
although the plurality of protrusions 30 herein are printed on the
principal surface 24a of the light guide member 20, the plurality
of protrusions 30 may be printed on the principal surface 24b of
the light guide member 20 or on both the principal surfaces 24a and
24b.
[0072] Typically, the light guide member 20 is made of acrylic
resin having high hardness. Further, typically, in the
manufacturing apparatus 200, the printing roll 210 is made of
metal, while the transfer roll 220 is made of resin. Accordingly,
since the transfer roll 220, rather than the printing roll 210,
comes in direct contact with the light guide member 20 in the
manufacturing apparatus 200, a physical impact on the acrylic resin
can be reduced.
[0073] Thus, the light guide plate 10 is preferably manufactured by
gravure offset printing. Gravure offset printing can reduce the
amount of use of the material for the protrusions 30 and can form
the protrusions 30 easily at high speed. Further, gravure offset
printing can obtain the minute protrusions 30 and can form the
protrusions 30 with a material different from the material for the
light guide member 20. However, even in gravure offset printing,
the protrusions 30 may be made of almost the same material as the
light guide member 20.
INDUSTRIAL APPLICABILITY
[0074] According to the present invention, the diffusion efficiency
of the light guide plate can be increased. The above light guide
plate may be suitably employed in liquid crystal display devices
and illumination devices.
Reference Sings List
[0075] 10 light guide plate [0076] 20 light guide member [0077] 30
protrusion [0078] 100 liquid crystal display device [0079] 110
light source [0080] 120 liquid crystal display element [0081] 130
reflector plate [0082] 200 light guide plate manufacturing
apparatus [0083] 210 printing roll [0084] 220 transfer roll [0085]
230 conveyance section [0086] 240 dryer
* * * * *